John M. Nugent Jr., a former Timmons and Co. vice president, pleaded guilty yesterday to a charge of aiding and abetting in the illegal trading of inside information, saying he had no idea that a friend would make a $250,000 profit after Nugent told him of a planned takeover.

Nugent told U.S. District Judge Barrington D. Parker that he was instructed by his superiors at the Washington lobbying and public relations firm not to disclose that the government of Kuwait was about to buy Santa Fe International Corp., a California oil products firm. Nevertheless, Nugent said he told his friend, Thomas A. Peacock, director of government relations for Wheelabrator-Frye Inc., of the planned takeover.

However, Nugent said in court that he had no idea Peacock made a profit by buying options to purchase Santa Fe stock after he learned of the impending acquisition in 1981. Nor was he aware of the law against disclosing insider information, he said.

Eleven Washington area residents, including eight local stock brokers, allegedly made a profit of more than $900,000 in one week as a result of the information passed along by Nugent and Peacock, according to U.S. Attorney Stanley S. Harris. Nugent could be jailed for up to five years, be fined up to $10,000, or both.